figure out if a simple polygon is valid

simple_polygon.rb

class Point
  attr_accessor :x, :y
end

class SimplePolygon
  def initialize(points)
    @points = points
    @lines  = []
  end

  def is_valid?
    i = 0
    while i < @lines.size
      intersects?(@lines[i], @lines[i+1])
    end

    true
  end

  def create_lines
    i = 0
    while i < @points.size
      @lines.append([@point[i], @points[i+1]])
      i += 1
    end

    @lines.append([@point.last, @point.first])
    @lines
  end

  def intersects?(line1, line2)
    return true
  end
end